The application relates to a rod-shaped implant in particular for stabilizing the spinal column and to a spinal stabilization device including such a rod-shaped implant.
EP 0 669 109 B1 discloses a stabilizing apparatus for stabilizing neighbouring thoracic vertebrae. The apparatus includes two monaxial pedicle screws and a strap that is fixed in the receiver member of each pedicle screw by means of a clamping screw and a support element that is mounted on the strap and is designed as a pressure resistant body. The stabilization apparatus, however, fails to be torsionally stiff and does not allow for axial extension. In addition, the use of monoaxial pedicle screws limits the application of this stabilization apparatus.
US 2007/0093820 A1 discloses a dynamic spinal stabilization comprising a flexible rod made of an elastomer material which is clamped in the receiving parts of monoaxial bone screws. EP 1 795 134 A1 and EP 1 900 334 A1 describe a spinal stabilization system with a flexible elastomer rod and polyaxial bone screws.
The dynamic stabilization systems comprising a flexible elastomer rod are suitable for the control, in particular the damping, of axial compression and extension of motion segments of the spinal column. The elastomer material is advantageous with respect to obtaining the suitable length of the rod-shaped implant by cutting an elastomer rod and the implant is simple to manufacture.
In clinical cases of early degeneration or partial damages or injuries of intervertebral discs the corresponding motion segments of the spinal column are subject to increased rotational movements and shearing forces. Such rotational movements and shearing forces can cause strong pain.
US 2007/049937 A1 discloses a rod-shaped implant which includes a metallic hollow rod with a flexible section in form of a helix-shaped recess in wall of the rod. In the hollow rod a longitudinal core is provided which can be fixed with respect to one end of the rod and which can be moveable with respect to the other end of the rod. The problem of kinking of the rod-shaped implant caused by shearing movements of the spinal column is considerably reduced.
Based on the foregoing, there is a need to provide an implant and a stabilization system for the spinal column which is particularly suited for cases in which rotational and shearing movements of the spinal column shall be suppressed.